Integral image elements which use a lenticular lens sheet or a fly's eye lens sheet, and a three-dimensional integral image aligned with the sheet, so that a user can view the three-dimensional image without any special glasses or other equipment, are known. Such imaging elements and their construction, are described in "Three-Dimensional Imaging Techniques" by Takanori Okoshi, Academic Press, Inc., New York, 1976. Integral image elements having a lenticular lens sheet (that is, a sheet with a plurality of adjacent, parallel, elongated, and partially cylindrical lenses) are also described in the following Unites States patents. U.S. Pat. No. 5,391,254; U.S. Pat. No. 5,424,533; U.S. Pat. No. 5,241,608; U.S. Pat. No. 5,455,689; U.S. Pat. No. 5,276,478; U.S. Pat. No. 5,391,254; U.S. Pat. No. 5,424,533 and others; as well as allowed U.S. Pat. No. application Ser. No. 07/931,744 now abandoned. Integral image elements with lenticular lens sheets use interlaced vertical image slices which, in the case of a three-dimensional integral image, are aligned with the lenticules so that a three-dimensional image is viewable when the lenticules are vertically oriented with respect to a viewer's eyes. Similar integral image elements, such as described in U.S. Pat. No. 3,268,238 and U.S. Pat. No. 3,538,632, can be used to convey a number of individual two-dimensional scenes (such as unrelated scenes or a sequence of scenes depicting motion) rather than one or more three-dimensional images.
Integral image elements using reflective layers behind the integral image to enhance viewing of the integral image by reflected light, are also described in U.S. Pat. No. 3,751,258, U.S. Pat. No. 2,500,511, U.S. Pat. No. 2,039,648, U.S. Pat. No. 1,918,705 and GB 492,186.
In a typical method of assembling a lenticular type of integral image element, an original negative is exposed from stored digitized data of a composite lenticular image on a film writer. A suitable film writer is the Symbolic Sciences International Fire 1000 and the LVT Model 1620B, available from Light Valve Technology, a subsidiary of Eastman Kodak Company, Rochester, N.Y. A suitable negative exposure technique is disclosed in U.S. Pat. No. 5,276,478. After photographic processing, the negative is printed, typically by a projection enlarger, onto a suitable film- or paper-based photographic print stock. After processing, the lenticular composite print is coated with adhesive, aligned with a lenticular lens sheet, and pressed against the lens sheet to permanently adhere to it in proper registration with the printed lenticular composite image. However, it is also known to write the lenticular image directly onto a back side of a lenticular lens sheet which is coated with a suitable receiving layer, such as disclosed in U.S. Pat. No. 5,349,419 and U.S. Pat. No. 5,279,912. Furthermore, such "writing" of the lenticular image can be temporary, as in a display produced on a CRT or Liquid Crystal Display ("LCD") screen immediately adjacent the back side.
Since each of the lenses of a lenticular lens sheet is dedicated to a single image set of interleaved image lines, it is important that the lenticules be rotationally and translationally positioned with the image line sets, so that each set is parallel and aligned with a corresponding lenticule. Schemes for rotationally and translationally positioning a print with an overlay are disclosed in U.S. Pat. No. 5,479,270. However, by writing the image directly on the back side of the lenticular lens sheet, as disclosed in U.S. Pat. No. 5,349,419 and U.S. Pat. No. 5,279,912, an alignment step of the written image with the lenticular lens sheet is avoided.
While the width of each set of image lines may be less than or equal to the width of a lenticule, and each may be centered under its corresponding lenticule, these conditions are not essential. For example, U.S. Pat. No. 5,278,608 and U.S. Pat. No. 5,276,478 describe methods in which the image sets become increasingly spaced from the centers of their respective lenticules moving from the center to the edges of the integral image element. What is typically required is that all of the lines from only a single image can be clearly viewed from an intended (that is, preselected) viewing position in front of the lenticular lens sheet. For individual integral image elements or for short runs (that is, only a small number of copies) of integral image elements, this has been accomplished in the known art by first accurately measuring the pitch of the lenticular lens sheet to be used. The pitch, which provides the number of lens elements over a given distance, is a measure of the size of the lenticular lens elements. The spacing of the sets of image lines in the print of the integral composite image would then be selected by a suitable magnification of the original integral image (whether optically or mechanically during printing from a negative, or electronically before printing an integral image in a computer memory). Following selection of the magnification, the print would then be printed directly onto the back side of the lenticular lens sheet or onto a separate substrate (such as photographic film) with the resulting print then being aligned adjacent the back side of the lenticular lens sheet.
Increasingly, it is desired to provide more image lines (such as 10 or more) within each image line set so that more images can be seen through the lens element (such as more views for a look-around capability or more frames in a motion image sequence). This means for such "higher density lenticular images" that for a given lenticular lens sheet, each image line becomes narrower. Because of this, accurate alignment of the image line sets with respective elements becomes even more critical.
It would be desirable then, to provide a means by which relatively accurate alignment of image lines with corresponding lenticules can be obtained, even with very narrow image lines.